The ready availability of a variety of highly flavorful food products coupled with the relatively sendentary lifestyles of a good segment of the population has given rise to an excess accumulation of calories in many people. Estimates indicate that currently as much as 40% of the U.S. application is overweight. J. Beereboom, CRC Critical Reviews in Food Science and Nitrition, 11(4), pps. 401-413, May 1979. Consequently, an increasing number of consumers are practicing some form of dieting and monitoring of caloric intake. This is evidenced by the successful introductions and rapid growth of a variety of reduced calorie products, such as cake mixes, beers, wines, candies and sodas into the food market.
Two of the most significant contributors to the population's calorie intake are sucrose (i.e., common table sugar) and high fructose corn syrup. In fact, a great deal of effort has been expended in the food sciences to develop a functional reduced calorie sugar substitute.
In 1985, the Calorie Control Council's brochure Sweet Choices described in ideal sweetener as having the following characteristics:
same or greater sweetness as sucrose PA0 colorless PA0 odorless PA0 readily soluble in water PA0 stable PA0 functionally similar to sucrose PA0 economically feasible PA0 contribute reduced or no calories to the diet PA0 non-toxic and non-promoting of dental caries PA0 combinations of bulk extenders and available artificial sweeteners PA0 modified sugars
The Council commented that up to that data a sweetener having all those characteristics did not exist.
Sugars are best known as sweeteners, however, their role as functional components in foods is equally important. Sugar influences many properties of food in addition to flavor. It alters the degree of hydration of many substances, influences the viscosity of starch pastes, the firmness of gelatin and pectin gels, and the formation and strength of gluten strands. It controls the gelatinization temperature of starch and the gelation temperatures of gluten and egg proteins. It affects the rate of spoilage due to the growth of micro-organisms. In many cases, it alters the color and texture of fruit products. It increases the moisture-retaining ability of many foods. The size of sugar crystals influences markedly the textural characteristics of candies and frostings and it enhances the body of beverages. (See Paul and Palmer, Food Theory and Applications, pp. 47 (1972)). All of these properties are regulated by varying the concentration of sugar in the food product. As a result, the volume fraction of sugar in foods is often very high. This is commonly referred to as sugar's bulking characteristic. One of the major problems in developing a reduced calorie sugar substitute is to provide this bulking characteristic.
Most artificial sweeteners in use today have a relative sweetness greater than sucrose; thus, relatively small quantities are required to deliver the desired sweetness. Such low volume sweeteners may be acceptable for certain applications (e.g., beverages), however, they do not provide sufficient bulk and functionality for use in solid and semi-solid foods like baked goods and frozen desserts. In fact, even high intensity sweetener-containing beverages have a detachable reduction in their body. Two avenues have been explored to overcome this bulking problem:
Presently-available sweeteners and sweetener/bulk extender combinations are not satisfactory due to their significant deviation from the important functional characteristics of sucrose (e.g., solubility and control of starch gelatinization), significant calorie values, and negative physiological effects.
Polydextrose, produced by Pfizer Corp., is a non-sweet, randomly bonded glucan containing small amounts of sorbitol and citric acid. It is presently the most widely used reduced calorie bulk extender in foods. As a sugar substitute it contributes 1 kcal/g, which is equivalent to about 25% of the calorie contribution of sucrose.
U.S. Pat. No. 2,876,105, Jucaitis and Biudzius, issued Mar. 3, 1959, discloses another class of carbohydrate polymers to be used as bulk extenders. Other bulk extenders include gum arabic and gum tragacanth. However, they are not desirable since they are not readily soluble, especially in cold liquids, and they have high relative viscosities and they have little control of starch gelatinization. See U.S. Pat. No. 3,704,138, LaVia, issued Nov. 28, 1972.
Arabinogalactan (Larch Gum) is a highly branched polymer of arabinose and galactose obtained from the Western Larch tree. Though it has FDA clearance for use in foods and has many suitable physical properties, such as good solubility in solutions having low viscosities, actual use has been small due to taste, functionality, heat-stability problems, and poor starch gelatinization control.
U.S. Pat. No. 4,207,413, Szarek et al., issued Jun. 10, 1980, discloses that L-sucrose (.alpha.-L-glucopyranosyl-.beta.-L-fructofuranoside) has identical sweetness to sucrose but is not metabolized on ingestion and is, therefore, non-caloric. The high cost of synthesizing this compound acts as a significant barrier to its development as a dietary sweetening agent. See Kirk-Othmer, Encyclopedia of Chemical Technology, third ed., vol. 21, pg. 939 (1978). A later patent discloses that L-monosaccharides are also edible and non-caloric (U.S. Pat. No. 4,262,032, Levin, issued Apr. 14, 1981). These L-sugars are also very costly to synthesize.
Sugar alcohols, called alditols, have also been proposed as sugar substitutes. However, only a few alditols have been approved as food additives and they have limited dietary applications due to their low laxative threshold and significant caloric value. (See, Rothschild, Food Chemical News Guide, mannitol, pg. 255 (1987); sorbitol, pg. 430 (1982); xylitol, pg. 495 (1986)).
In order to test structure-sweetness correlations, Witczak and Whistler, Carbohydrate Research, 169 (1987), 252-257, synthesized many compounds, including a large group of compounds including the branched-chain alditol, 2-C-(hydroxymethyl)-D-mannitol. Witczak and Whistler did not comment on the metabolizability of compound.
U.S. Pat. No. 4,459,316, Bakal, issued Jul. 10, 1984, teaches that di- and trisaccharides containing one levohexose component and at least one dextrohexose component (e.g., .alpha.-L-glucopyranosyl-.beta.-D-fructofuranose) are non-caloric. These disaccharides are costly to synthesize due to the fact that they are prepared from a racemic mixture of D-hexoses and expensive L-hexoses.
Thus, there has not yet been developed in the art a sugar replacement component which is low in calories, inexpensive to synthesize, sweet, functional (especially as a bulking agent) and avoids negative physiological effects. It would be highly desirable to define such a compound.
It has been found (U.S. patent application, Ser. No. 190,486, filed May 5, 1988 by Mazur) that derivatives of 5-C-hydroxymethyl-D-hexose compounds can be used as replacements for sugar, especially in baked goods. These carbohydrates provide sugar-like functionality (i.e., bulk, texture and stability) with significantly reduced calories compared with sucrose. It has also been shown that saccharides containing a 5-C-hydroxymethyl-D-aldohexosyl or 5-C-hydroxymethyl-D-ketohexosyl component provide similar benefits. This also holds true for the alditols of these carbohydrates, 5-C-hydroxymethyl-D-aldohexosyl polyol derivatives, alkyl derivatives of the carbohydrates (i.e., alkyl 5-hydroxymethyl-D-aldohexoside or alkyl 5-hydroxymethyl-D-ketohexoside), and 1,6-anhydro-.beta.-D-, and 1,6-anhydro-.beta.-L-derivatives of the pyranose compounds (i.e., the bicyclic tautomeric forms).
Galactose oxidase has the particular characteristic of converting the C-6 hydroxy group in galactose to the corresponding aldehyde (See Mardufu et al., Can. J. Chem., 50, 768 (1971)). The reaction has been successfully applied to a number of mono- and polysaccharides (See Whyte et al., Carbohds. Res., 57, 273 (1977); Jacket et al., Carbohds. Res, 49, 335 (1976)). Root et al., J. Am. Chem. Soc., 107, 2997 (1985), have recently shown that this enzymic synthesis can be applied to polyols. Also, Yalpani and Hall, J. Poly. Sc., 20, 3399-3420 (1982), have cataloged a significant number of applications for the product of the galactose oxidase reaction (e.g., reductive amination, oxidation and reduction).
Schaffer, J. Am. Chem. Soc., 81, 5452 (1959), teaches that 4-hydroxymethyl pentose may be condensed from its corresponding aldehyde with formaldehyde in aqueous sodium hydroxide. This reaction has recently been applied to other sugars (See Carbohds. Res., 38 (1974), pp. C9-C11 and J. Org. Chem., 44 (8), 1301-1317 (1979)).
It has now been found that the 5-C-hydroxymethylation of D-aldohexose compounds, D-aldohexosyl functional groups and D-aldohexoside functional groups, can be accomplished by an enzymic conversion reaction followed by a condensation reaction with formaldehyde. This reaction provides a functional sugar replacement (i.e., a 5-C-hydroxymethyl-D-aldohexose-based compound in a very economical manner.